As Kathleen Folbigg awaits an inquiry into her convictions for killing her four young children, medical experts are coming forward to say that in their opinion, her fourth child Laura died from natural causes.

Key points:

Kathleen Folbigg found guilty in 2003 of murder of three of her children and manslaughter of another

She is serving a 30-year sentence

Inquiry into convictions announced by NSW Attorney-General in August

And now a friend of Ms Folbigg's has recounted a frightening incident involving Laura.

Karren Hall has been a friend to Ms Folbigg since 1994, when three of her children had already died.

When Ms Folbigg's fourth child Laura was born, she offered to help, and in addition, arranged to be trained in CPR.

"I went and did a course on resuscitation for babies," Ms Hall told the ABC.

"I took every precaution that I could think of. Because she wasn't gonna go on my watch."

When Laura was about 12 months old, Ms Hall took her home to babysit while Ms Folbigg ran some errands.

Laura fell asleep on her couch, and about 20 minutes later the phone rang.

"It was Kath, checking on Laura to make sure she'd behaved herself or was doing all right," Ms Hall said.

When Ms Hall returned to check on Laura, she was shocked.

"She was a funny colour, like it had drained," Ms Hall said.

"I actually got on the floor and bent over. I couldn't hear her breathing, couldn't feel her breathing. I sort of went into panic mode. I put my arms under her and scooped her up and was about to put her on the floor to start CPR, and she took a big in and then a couple of breaths, and it was all good from there.

"But it was very scary. I believe she had stopped breathing. I did everything that I was trained to do to see whether she was breathing or not, and to me there was no breath, none at all."

Ms Hall gave evidence at Ms Folbigg's trial where, under questioning by the Crown prosecutor, she conceded she couldn't say for certain Laura wasn't breathing.

'The colour change is significant'

Dr Matthew Orde is a forensic pathologist at Vancouver General Hospital, and a clinical associate professor at the University of British Columbia, in Canada. He has reviewed the evidence in Laura's case and told the ABC it is possible Laura suffered an acute, life-threatening event, or ALTE.

"The episode described by Karren Hall, when Laura was 12 months of age, could well be an ALTE," he said.

"It seems to me that she stopped breathing, even if that's temporarily. But the colour change is the significant thing here. So it may well have been a very significant event."

Eight years before, Ms Folbigg's second child Patrick had suffered an acute, life-threatening event which left him brain-damaged. Four months after that, he died.

At her trial in 2003, the jury decided Ms Folbigg had smothered all four of her children and that she had twice attempted to smother Patrick.

But Ms Hall's experience with Laura raises the possibility Ms Folbigg's children had a genetic abnormality which rendered them at risk of sudden death.

At a directions hearing in Sydney earlier today, the presiding judge, Reginald Blanch, said he had seen a transcript of a meeting of geneticists which took place earlier this week to discuss the case, and that, "it raises the possibility of some new evidence that could lead to the exculpation of Ms Folbigg".

The court heard a DNA sample had already been provided by Ms Folbigg for genetic testing. The inquiry will ask her former husband, Craig, to provide a sample as well.

Expert says there's no evidence of homicide

Meanwhile, a confidential briefing note written by one of Australia's top forensic pathologists has been obtained by the ABC which raises fresh questions about the conviction of Ms Folbigg in 2003 for smothering all four of her children: Caleb, Patrick, Sarah and Laura.

The note was written in 2015 by Professor Johan Duflou, a former clinical director of the Department of Forensic Medicine in Sydney, when he was asked to comment on an extensive review of the forensic evidence in the case which had been assembled by Professor Stephen Cordner, the former head of the Victorian Institute of Forensic Medicine.

Professor Cordner, in his 2015 review, concluded: "If the convictions in this case are to stand, I want to clearly state there is no pathological or medical basis for concluding homicide. The findings are perfectly compatible with natural causes.

"The findings cannot rule out smothering in one or more of the cases, but especially in the case of Laura, not only is there an acceptable natural cause of death easily visible microscopically, it is important that there are neither general nor specific signs of compression of the face present.

"Put simply, there is no positive forensic pathology support for the contention that any or all of these children have been killed.

"When it is all pared back, the medical evidence at the trial consists of four unexplained deaths [and an acute, life-threatening event] in one family which in the view of the doctors were, with no actual tangible evidence, likely to be four murders [and a very serious assault] by smothering."

One doctor who came in for particular criticism from Professor Cordner was Dr Allan Cala, who performed the autopsy on Laura. Dr Cala found some evidence of myocarditis, a potentially fatal inflammation of the heart muscles, when carrying out his autopsy, but gave the cause of death as "undetermined".

At Ms Folbigg's trial, he said he did not believe myocarditis played any role in causing her death.

Professor Cordner noted: "Dr Cala was of the view that Laura died with myocarditis rather than from it, but his reasons for this do not hold water in my view."

He said that where Dr Cala had described the myocarditis as "patchy and mild; I think it is better described as widespread and at least moderate in degree".

"I do think Dr Cala could have justified the cause of death as he gave it: Undetermined. He was incorrect to argue that there were medical and pathology reasons for excluding myocarditis."

View 'would not be shared by most forensic pathologists'

In June 2015, Professor Duflou was asked to provide dot points from a clinical perspective as to what implications Professor Cordner's report could have on Dr Cala, who was one of the key expert witnesses at Ms Folbigg's trial. The request came from a senior colleague who was preparing a brief for the chief executive of NSW Health Pathology.

In his note, Professor Duflou commented: "The report by Professor Cordner implies strongly that Dr Cala has not been impartial in his assessment of Laura's death. In my opinion, there is definite myocarditis present, and this could reasonable [sic] have been the cause of death.

"Given the preceding events in this family, however, I am of the view that the cause of death was reasonably attributed by Dr Cala as 'Undetermined'. However, I share Professor Cordner's opinion that Dr Cala's view on the likelihood of death not being due myocarditis is one that would not be shared by most forensic pathologists."

In a later comment, Professor Duflou went further, saying: "I therefore agree with the implicit views of Professor Cordner that there may have been bias on the part of Dr Cala."

Claim of confirmation bias

"I'm a scholar of bias. Research in cognitive science shows that when someone believes that there is a likely explanation for a phenomenon that they are observing, they are more likely to notice evidence that supports their conclusion, and less likely to notice evidence that can test their conclusion," Ms Cunliffe told Australian Story.

"This is what leads to the definition of confirmation bias, and I believe that Dr Cala may well have fallen prey to confirmation bias in the way in which he testified in the Folbigg case.

"Confirmation bias is a difficult and subtle phenomenon, something that is not observable, by definition, to the person who experiences it. It is something to which everyone is susceptible in the right conditions.

"This was a case that would have been extremely difficult for those who were involved in it. Dr Cala was presented with an autopsy of a 19-month-old girl, in a context in which he knew there had been other deaths in the family.

"He was working closely with the police, speaking regularly to them while the investigation was taking place. I believe that the information he had about the police suspicions may have influenced his medical judgement on the things that he could observe on autopsy."

Call for all four autopsies to be reviewed

Professor Duflou's opinion, the ABC understands, is shared by another former clinical director at the NSW Department of Forensic Medicine, Professor John Hilton. Professor Hilton was Dr Cala's boss at the time he performed his autopsy on Laura Folbigg.

Professor Hilton gave evidence at the trial, after determining at autopsy that Ms Folbigg's third child, Sarah, had died from SIDS.

The ABC understands Professor Hilton has sworn an affidavit for the judicial inquiry into Ms Folbigg's convictions, in which he says he would not have found Laura's cause of death was "undetermined".

The ABC understands Professor Hilton says he would have concluded the cause of Laura's death was myocarditis, and that, if he had carried out the autopsy, he would have written "myocarditis" as the cause of death.

Earlier this year, at the ABC's request, Dr Orde examined the microscopic slides of Laura's heart and reached the same conclusion as Professors Hilton and Cordner.

Dr Orde told Australian Story: "I think this is an eminently fatal case of myocarditis. Of course we can't say for sure that this would have been the cause of death in Laura's case. All I can say is I think this provides a very good explanation for her untimely death."

In the note he wrote for his colleagues at NSW Health Pathology in 2015, Professor Duflou said: "It is strongly recommended that all four autopsies be reviewed in detail, in anticipation of this being required at some time in the future. This would have significant resource implications, given the large amount of material involved in the case."

By this time, Ms Folbigg had already spent 12 years behind bars.

However, the ABC understands that to date, Professor Duflou's recommendation has not been acted upon and his note has not been made public.

A spokesperson for NSW Health said the briefing note "has been produced to the inquiry".

Ms Folbigg invited to give evidence

At today's directions hearing, counsel assisting the inquiry, Gail Furness SC, said the full hearings will begin on Monday March 4, 2019, when evidence on the forensic pathology in Ms Folbigg's trial will be presented.

Two weeks later, evidence will be presented relating to SIDS and cardiology. And two weeks after that, on Monday April 1, evidence will be presented relating to the genetic evidence.

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